Area Forecast Discussion
Issued by NWS Sterling, VA
FXUS61 KLWX 211413 AAA
Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
1013 AM EDT Wed Sep 21 2016
High pressure will build over the region through Thursday. A cold
front will move through the area Saturday. High pressure builds
again over the region early next week.
.NEAR TERM /THROUGH TONIGHT/...
GFS not doing particularly well with extent of high clouds this
morning. ECMWF and HRRR simulated cloud imagery doing much better
and have followed their output closely. Expect current extent of
high clouds to remain pretty much as is through midday with
thining of high clouds in the afternoon and clouds shifting south
and east by evening. Adjusted temps a bit based on model trends
from ECMWF indicating a 2-3 deg rise from yesterday in the east
with temps west of the Blue Ridge not showing any trend at all
from yesterday. Showers to graze southern St. Marys county through
the day with precip shifting south tonight.
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Onshore NEly flow persists Thursday with above normal temperatures,
mid 80s, under mostly sunny skies as cloud shield looks to be along
southern periphery of the CWA.
Surface high pressure settles south over the area Friday with sunny
skies and light/variable winds. Maxima mid to upper 80s.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
A transition to autumn weather will occur over the weekend after a
cold front tracks down from the north Saturday afternoon. This is
a dry trajectory...so don`t expect much if any rainfall with this
system. After reaching 80 degrees Saturday it does not appear the
area will be seeing that for the next several days. Sunday highs
will likely only reach the mid 70s but the real story will be
Sunday night/Monday morning when lows east of the mountains will
drop into the lower 50s...and likely 40s in the Highlands.
By Tuesday some warming to the atmosphere should take place ahead
of a cold front. This will likely provide the next chance for rain
to the Mid Atlantic.
In somewhat of a coincidence..at IAD both since Sep 1 and Jan 1
the precipitation departure from normal is -2.21".
.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
High cloud shield persists over the area from low pressure
lingering along the NC coast. This is limiting fog development
across the DC metros. Best fog chance through sunrise is at MRB
though high clouds are currently over that area too.
VFR conds prevail through Friday high pressure slowly settles south
over the area.
VFR conditions expected this weekend.
NEly flow 10-15kt down the main portion of the Bay through Thursday
as low pressure lingers along the Carolina coast. Weak Nly flow
Thursday night through Friday as high pressure settles south over
Winds could increase to near SCA values near/behind a cold front
Saturday into Sunday.
Elevated water levels persist through the rest of the week due to
low pressure off the Carolina coast. Coastal flooding threat is low